1. Field of the Invention
The present invention relates to a component mounting board inspecting apparatus for inspecting for defects in cream solder printed on an electrode pad of a component mounting board, and, more specifically, inspecting whether there are solder bridges generated between adjacent electrode pads.
2. Description of Related Art
On a component mounting board, such as a printed board for mounting a number of components of a semiconductor device and the like, a number of electrode pads corresponding to the number of electrodes of these components, and a wiring circuit pattern are formed. In order to solder these components cream solder is printed on the electrode pads by a screen printing method, for example. If the cream solder is not suitably printed on the electrode pads, the components cannot be desirably soldered. Therefore, before soldering the components on the component mounting board, the board is inspected for whether or not the cream solder is suitably printed on each electrode pad by the use of a component mounting board inspecting apparatus.
A functional block diagram of such a component mounting board inspecting apparatus is shown in FIG. 4, in which reference numeral 100 indicates a component mounting board inspecting apparatus. The component mounting board inspecting apparatus 100 has an annular illuminating apparatus 110, a camera 120, such as a CCD camera, an image processor 130, a control unit 140, and a result indicator 150.
The illuminating apparatus 110 facilitates observation of a component mounting board B. The camera 120 captures a visual image of the component mounting board B illuminated by the illuminating apparatus 110. The image processor 130 captures the image outputted from the camera 120, and then executes an inspection algorithm. The control unit 140 controls the brightness of the illuminating apparatus 110, and the drives of the illuminating apparatus 110 and the camera 120. The result indicator 150 indicates an obtained inspection result.
A method of determining whether cream solder is suitably printed or not is as follows: the printed state of the cream solder on the component mounting board B is compared with the information captured by the image processor 130, based on the information of printing of cream solder (the printing area of the cream solder, the printing width of the cream solder, and the printing position of the cream solder), which are preset in the component mounting board inspecting apparatus 100.
In the cream solder inspection method, the object to be inspected is solder subjected to reflow, instead of cream solder. This kind of inspection is disclosed in Japanese Patent Application Laid-Open No. 10-160426 (page 1, and abstract), for example.
A variety of electrode pads are formed on the component mounting board B, such that a variety of components, including various semiconductor devices, are mountable thereon. A plurality of electrode pads 1A, 1B, 1C, . . . , are formed in a predetermined array on the component mounting board B, and the pad-to-pad distance of these electrode pads will vary over different portions, as partially shown in FIG. 5 (electrode pads having a large pad-to-pad distance are not shown). Referring to FIG. 5, the pad-to-pad distance of the electrodes pads 1A, 1B, 1C, . . . , which mount, for example, a ball grid array (BGA) type IC and a quad flat package (QFP) type IC, is considerably narrow (or, short), for example, about 500 μm or less. When cream solder S is printed on the electrode pads 1A, 1B, 1C, by a screen printing method, etc., as shown in FIG. 6, it is desirable that the cream solder S is printed so as not to spread beyond the electrode pad 1B. However, as shown in FIG. 7, the cream solder S on a certain electrode pad, for example, the electrode pad 1A, may bridge the electrode pad 1B adjacent to the right side. This is a so-called solder bridge Sb. Needless to say, the occurrence of the solder bridge Sb is undesirable, and hence this must be reliably detected, and the component mounting board B involving the solder bridge Sb must be removed from the line.
Conventionally, in creating an inspection program for detecting the solder bridge Sb between the pads at which a solder bridge Sb is likely to occur, an operator manually sets a bridge inspection point Pb indicated by the dotted lines, which is extended to electrode pads adjacent to an inspection point Pa for observing the electrode pads 1A, 1B, 1C, . . . . There is no need for setting the bridge inspection point Pb between electrode pads having a large pad-to-pad distance D, and it is only necessary to set the inspection point Pa at which the state of the cream solder S on each electrode pad is observed.
Consequently, if an operator performs an inspection without making any manual setting, despite a defect due to a solder bridge, this may be detected as another kind of defect, or maybe even overlooked.
In addition, there are the following limitations: with respect to a solder bridge inspection region, it is required to indicate the inspection point Pb individually as above described; and the inspection point Pb can be pasted (copied) only to the same pattern on the component mounting board B. Thus, a considerable amount of time is required for creating data designating a solder bridge inspection region (an inspection point) Pb.